Micromachined sensors and actuators (sometimes referred to as microelectromechanical systems or MEMS and micro-opto-electro-mechanical systems or MOEMS) are made using semiconductor technologies so these microstructures have very clean surfaces. Inorganic surfaces that are extremely clean tend to stick together if they come into contact. If microstructure surfaces stick, the device becomes defective. One example of such a component is the class of inertial microsensors that measures acceleration and deceleration (e.g., an accelerometer), and an example of one of these is the sensor which determines whether an automobile is colliding and the air bag should be deployed. Another example is a gyroscope. A third example, representing non-inertial micro-structures, is a micro-mirror array such as that used in optical communications and projection systems.
The airbag sensor has a sub-component which moves in response to the inertial changes that arise during rapid deceleration. The failure of this subcomponent to move during deceleration can be caused by the sticking of this micro-subcomponent to other components in its immediate environment. This concept of sticking is called “stiction”, and the concept of preventing sticking from occurring is called “anti-stiction”.
There has been some prior development of anti-stiction treatments that are applied during assembly and packaging. For example, U.S. Pat. No. 5,694,740 (hereafter referred to as '740) describes the vapor deposition of various organics, including silicones, alkoxysilanes and perfluoroethers, to the component during assembly. Although this treatment reduces stiction, it is not efficient to treat each individual component, since these electronic components are extremely small, and large numbers of these components are manufactured at one time. Fluorocarbons, also applied during assembly, have been used as anti-stiction treatments for micro-optical devices (based on the concept of a light beam being deflected by a moving mirror) in U.S. Pat. No. 5,936,758.
Anti-stiction treatments normally “passivate” the surface and are called passivants. That is, they alter surfaces to make them less interactive with their surroundings.